Question

Which reactions are oxidation-reduction reactions? Check all that apply.

2 upper N a plus upper C l subscript 2 right arrow 2 upper N a upper C l.

Upper P b (upper O upper H) subscript 2 right arrow upper P b upper O plus upper H subscript 2 upper O.

Upper C u plus 2 upper A g upper N upper O subscript 3 right arrow upper C u (upper N upper O subscript 3)subscript 2 plus 2 upper A g.

Upper Z n upper B r subscript 2 plus 2 upper A g upper N upper O subscript 3 right arrow 2 upper A g upper B r plus upper Z n (upper N upper O subscript 3) subscript 2.

Upper C upper H subscript 4 plus 2 upper O subscript 2 right arrow upper C upper O subscript 2 plus upper H subscript 2 upper O.

Answer 1

Redox reactions: 1, 3, and 5.

Brief justification:
- 2 Na + Cl2 → 2 NaCl: Na 0 → +1 (oxidation), Cl 0 → -1 (reduction).
- Pb(OH)2 → PbO + H2O: oxidation states unchanged (Pb stays +2) — not redox.
- Cu + 2 AgNO3 → Cu(NO3)2 + 2 Ag: Cu 0 → +2 (oxidation), Ag +1 → 0 (reduction).
- ZnBr2 + 2 AgNO3 → 2 AgBr + Zn(NO3)2: oxidation states unchanged (no redox).
- CH4 + 2 O2 → CO2 + 2 H2O: C -4 → +4 (oxidation), O2 0 → -2 (reduction).